particular instance, however, much of the variability is attributable to the insensitivity of the analytical methods to accurately measure the low levels of Pu and Am radionuclides present in the small samples of vegetation available for radioassay. In spite of the high degree of variability, these results gave some interesting findings. First, the uptake of Pu and Am radionuclides through plant roots was relatively low compared to the levels of contamination present in the soil. CR values for 239°2"9Pu ranged from 107° to 107? for barley forage and from 10-© to 10°? for the fruit heads. In several cases, the CR values for **!Am were within an order of magnitude higher than for Pu, indicating greater uptake of Am in proportion to Pu uptake through plant roots. Second, the nitrogen fertilizer and organic matter amendments had no significant influence on root uptake of these radionuclides. The DTPA chelate treatments showed a tendency for increased uptake, but the high variability masked any test for significance. Third, the acidulation effect of sulfur in combination with DTPA chelate significantly increased (P = .05) plant uptake of 239°240py and 24 lam through roots. This might imply greater solubility of the source materials under more acidic edaphic conditions, but such conditions are unlikely to occur in the soils of aged fallout areas at NTS and TTR because of their high buffering capacity. Results from the second experiment with alfalfa plants are given in Table 4. Inasmuch as three different cuttings of forage were pooled together, the sample size available for radioassay was as much as 10 times that obtained from the single barley crop. Consequently, more reliable results were obtained with less variability in the analytical data. The results for alfalfa again verified relatively low plant uptake through roots of 239°240py and 24am from Area 13 soils. There were also no significant effects of the soil amendments applied without DTPA chelate, with the exception of an increase in 24 lam uptake attributable to acidulation by sulfur. For treatments where DTPA chelate had been applied, a significant increase (P = .05) in root uptake of Pu and Am radionuclides was induced by acidulation with sulfur. This particular effect was more pronounced for Pu than for Am uptake. The organic matter amendment in combination with DTPA chelate also significantly increased 239°240py uptake through alfalfa roots. However, part of this particular increase might have resulted from the slight acidulation effect caused by the high organic Matter treatment (pH 7.6 to 6.5). Even though certain modifying effects of soil amendments mentioned above were significant, from a practical standpoint, the CR values for Pu were altered only from 10-° to 107% and from one to two orders of magnitude higher for Am. Results are given in Table 5 for the third experiment wherein root uptake of Pu and Am from different fallout area soils was tested with soybean plants. (Analytical data for wheat grown in this experiment were not available to include in this progress report.) The 239°240py and 24!am contents of plant tissues varied among the different soils according to differences in the contamination levels present. Inasmuch as a common level of contamination had not been achieved, comparisons between data can be made only for the DTPA chelate and nonchelate treatments for a given soil. A simple test of these data indicated that, in virtually all cases, the addition of DTPA chelate significantly increased Pu and Am radionuclide uptake through soybean roots. Among the different soils tested, higher levels of Pu and Am activity appeared to be taken up from the Area 11C and D soils in proportion to the contamination 59